Method of forming alpha die mounting



Patented May 22, 1934 UNITED STATES 1,959,422 METHOD or FORMING A DIE MOUNTING Robert A. Harris, Oak Park, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application January 8, 1930, Serial No. 419,433 1 Claim. (01. 76-107) This invention relates to a' method of making a die mounting, and more particularly to the method of forming a wire drawing die mounting. It has been a practice in some instances, in l mounting working elements such as wire drawing dies, to position the element in a mold, surround the element with a metallic dust, such as finely divided nickel-iron alloy, fuse the finely divided metal and permit the molten material encasing the element to cool slowly to complete the mounting of the element.

Objects of this invention are to'provide an efiicient and durable mounting fona working element, and a method of formingsuch a mounting which will be simple, efiective and economical. In accordance with the general features of the invention, a mold is partially filled with a. quantity of permalloy dust and a partially bored diamond is centered with respect thereto and additional permalloy dust placed therein to fill the mold chamber. Pressure is then applied to cause the dust to flow and form in a cake around the diamond, after which the cake is removed from the mold and heated to sinter the dust into a solid envelope for the diamond. This envelope is then pressed into a bronzemounting and drilled to expose the diamond, the bore of which is subsequently drilled to working size. A thorough understanding of the invention is afiorded by the following detailed description,

read in connection with the accompanying drawing forming a part thereof, in which Figs. 1, 2 and 3 are complementary sectional views of an apparatus whereby successive steps of the methods maybe performed, and

Fig. 4. is an enlarged perspective view of a mounted die completed in accordance with one embodiment of the invention.

Referring to the drawing in which similar 40 parts are indicated by identical reference numerals, the methodmay be carried out by means of a mold which includes a cylindrical plunger 10 mounted upon a circular base 11 and having an intermediate tapered portion 12. Superposed upon the basell and concentric therewith is an annular ring 14 composed of rubber or other resilient compressible material, the ring being of a thickness equal to the vertical extent of the tapered portion 12. An annular metal ring 15 has a central aperture 16, an upper porf the plunger 10. The parts named are. assembled as shownin Fig. 1, the flexible ring 14 being placed upon the base 11 with the metal ring 15 superposed thereon and receiving the plunger 10 within its central aperture 16. It will be understood that the plunger 10 in such a position closely engages the sides of the central aperture 16 so as to give a substantially pressuretight fit therebetween. When thus assembled,

it will be noted that the plunger 10 extends only 5 part way to the top of the metal ring 15, being prevented from doing so by the flexible ring 14 which maintains themetal ring in an elevated position with reference to the plunger 10 to permit the upper portion of the'aperture 16 to 7 form a mold chamber into which is poured a quantity of a finely divided metallic dust such as ordinary nickel-iron, permalloy or other metal or alloy having a low coefiicient of thermal ex pansicn, to approximately half fill the remaining 7 portion of the aperture 16. ,In this connection, good results have been obtained with finely divided permalloy, a nickel-iron alloy wherein the nickel content may vary from 25 percent to percent of the whole. go

A centering tool consists of a cylindrical plug 23 of a diameter to permit it to fit snugly in the aperture 16. The plug 23 is provided with a fine central aperture 24 and a threaded projection 26 of a lesser diameter than the plug proper, and an elongated tube 27, one end of which is internally threaded at 28 to correspond and cooperate with the threaded projection 26-01 the plug, is fitted thereto. A slender rod or pin 30 of a length sufiicient to permit it to ex- 9 tend beyond the tube 27 on the one hand and "the plug aperture 24 on the other is passed axially through the tube 27' and the aperture q 24. Upon that end of the pin 30 which projects from the tube 27, a handle 31 of any suitable type is provided. For centering a diamond, carborundum or other suitable working element 32, the element is partially shaped or drilled to provide an aperture 34 therein of such a dimensionas to permit the pin 30 to be wedged thereto with a relatively small amount of efiort on the part of an operator and which will yet.

permit their separation without great difficulty. Accordingly, the pin 30 is grasped at the handle 31-, passed through the tube 27 and forced through the relatively narrow aperture 24 of the plug and permitted to project therebeyon'd a distance suflicient to allow the pin to'be wedged into the aperture 34 of the working element, after which the pin 30 is gradually withdrawn until the working element 32-'-is brought flush with the bottom of the plug 23 (Fig. 1). By this means, the operator is enabled to accurately center the working element with reference to the mass of the metal dust 20. Releasing the handle 31 the operator then grasps the sleeve 27 and presses it downwardly and with a rotary motion in order to embed the working element in the metallic dust, at the same time compacting the metallic dust closely around the surfaces of the working element. While the plug 23 is held in the aperture 16, the pin 30 is withdrawn, and the plug 23 is subsequently withdrawn leaving the working element 32; embedded in the metallic dust. A sufficient quantity of metallic dust is then poured on top of the compacted mass to fill the aperture 16 to the level of the ring 15. A fiat circular plate 35 is then placed on top of the ring 15 cencentric therewith, and a downward pressure exerted on the mold, causing a movement of the plate 35 toward the plunger 10 and the compression of the resilient member 14 to the extent by which the cubical content of the mold chamber is reduced through the resulting compression of the metallic dust (Fig. 3). It has been found that a unit pressure of 200,000 pounds, applied for 2 hours, is sufiicient'to cause permalloy dust to fiow and form a self-sustaining supporting body or cake of metal, encasing the working element 32 therewithin and contacting intimately with every portion of the surface of the working element. The mold is then removed from the press, the plate 35 removed and the supporting body 20 ejected from the tapered portion 1'7 of the aperture 16. The supporting body 20 is then placed in a furnace .in a neutral atmosphere and subjected to a temperature sufficiently high to sinter the metallic dust comprising the supporting body. In the case of permalloy dust, a temperature of 2000 F. is sufficient to sinter the supporting body without deleteriously effecting the working element. Where finely divided material other than permalloy dust is employed it may be desirable in someinstances to vary the temperature and apply a pressure as determined by the particular metal or. alloy. This, however, would be a measure of convenience the desirability of which may be readily determined by experiment, and the stated values are accordingly not intended to be exclusive of others. Under certain circumstances other pressures may be employed to produce the desired mechanical properties of hardness, strength and toughness. It has also been found that pressures between 50,000 and 200,000 pounds per square inch may be used to obtain a very satisfactory die mounting possessing the desired properties. In any event the pressure to which the metal or alloy is subjected will be determined by the final mechanical property or properties present in the die mounting.

After slowly cooling, it will be found that the cake of metallic dust surrounding the working member has been changed to a solid supporting member 20 within which lies the working element 32, with every portion of its surface in intimate contact with the surrounding metallic body. After cooling, the supporting structure is mounted with a conventional type of bronze casing 36 or a suitable acid-resisting casing may be employed. The working element is then exposed by drilling or otherwise shaping the supporting structure to form oppositely extending funnel shaped openings 33-38 .(Fig. 4) from side to side thereof, after which the working element is completely bored to the desired size for wire drawing.

Practice of the described method is productive of a die mounting which is valuable for several reasons. The intimate contact between the metal of the solid supporting structure and the working element insures the very best support for the element, which is seldom obtained in the conventional types of hot or cold pressed or molten cast mountings. The liquid or fiowing action of the dust during pressing makes it impossible to crack a working element during pressing regardless of its shape, and does away with the hitherto customary hot pressing of the supporting body to insure an intimate contact between the element and the metal supporting body. By securing the intimate contact between the dust and all surfaces of the working element by subjecting the material to a relative high pressure and then sintering the mass by heating, an appreciable reduction in the crackage of working members in service is achieved, besides enabling the use of smaller working elements than has heretofore been found practicable. Furthermore, since the dust flows into and fills all the crevices in the surface of the element, it for the first time is made perfectly feasible to employ unsymmetrical working elements as 'well as fairly regular working elements in the same type of mounting.

It is obvious that numerous changes both in the character and order of the steps described above might be practiced without departing from the spirit of my invention and it should therefore be limited only by the scope of the appended claim.

What is claimed is: I 4

A method of mounting a die core which consists in centering the core with respect to a mass of finely divided nickel-iron alloy, enveloping the core therein, applying pressure to cause the particles to cold flow and intimately contact with the entire surface of the core, subjecting the mass to a temperature of approximately 2000" F. to sinter it and form thereof a solid enveloping supporting structure for the core and thereafter drilling the structure and core to produce a drawing die.

ROBERT A. HARRIS. 

